1. Field of the Invention
The present invention relates to a carrier film into which a semiconductor device is suitably mounted at high-density and to a process for producing the same.
2. Description of the Related Art
As a carrier film into which the semiconductor device is mounted, there is a conventionally known carrier film as disclosed in pages 727 to 732 of the 46th Electric Component & Technology Conference, for example. FIG. 1 is a schematic sectional view showing such a construction. In FIG. 1, tape matrix 34 comprising a copper wiring pattern 31, a base layer 32 made from polyimide film, and a bonding layer 33 made from thermoplastic polyimide film is provided with a bump 35 for electrical connection to a chip, and a cover resist layer 37 having openings 36 for electrical connection to a substrate to be mounted is defined on the copper wiring pattern 31.
In the carrier film having the above construction, quality of material and forming conditions of the cover resist layer 37 have a great influence on process margin and reliability in assembly of the semiconductor device. Properties required for the cover resist layer 37 are heat resistance, moisture resistance, close-contact property, chemical resistance in a plating process or the like, and smaller contraction in hardening of resin to prevent warping of the carrier film. Furthermore, in order to keep up with refinement of openings 36 due to increased number of pins in the semiconductor device, it is desirable to form the cover resist layer 37 in exactly the same exposure and developing process as those for a normal photoresist.
Epoxy acrylate resin or polyimide resin disclosed in Japanese Patent Application Laid-open No. 6-230571 or Japanese Patent Application Laid-open No. 8-50353, for example, is known as material of the cover resist. However, the conventional epoxy acrylate resin does not have sufficient heat resistance, causing degradation in insulation due to sag of pattern or carbonization in an assembling process of the semiconductor device. Further, the conventional epoxy acrylate resin does not have sufficient moisture resistance and chemical resistance and can not form a reliable semiconductor device. On the other hand, the polyimide resin has sufficient heat resistance of 300.degree. C. or more. However, the polyimide resin contracts largely at the time of hardening to cause warping, and is necessary to be heated at temperature of as high as 300.degree. C. or more for hardening, such heat degrading the bonding layer 33. For the above reasons, it is very difficult to apply the polyimide resin to the carrier film.